Y. Bellouard, T. Lehnert, R. Clavel, T. Sidler and R. Gotthardt, "Laser annealing of shape memory alloys : A versatile tool for developing smart micro-devices," Le Journal de Physique IV 11, Pr8-571 (2001).
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From a shape change point of view, the shape memory effect is not intrinsically reversible. Therefore developing Shape Memory Alloys (SMA) actuators, i.e. devices producing a motion, requires a suitable method to bypass this intrinsic property. Since the shape memory effect discovery, different methods, either intrinsic like the "Two-Way Shape Memory Effect" or extrinsic like the use of a biasing element have been investigated. In this paper, a new method based on a local annealing of the material is presented. A laser is used to locally crystallise amorphous thin film or re-crystallise cold-worked sheet of SMA material. For instance, this method allows the development of highly integrated micro-devices made out of one single piece of material. The basic principle, a typical setup and some effects of the laser annealing on the material properties are presented followed by some examples of monolithic micro-devices developed using this concept. (Download / PDF)